netns: selective flush of rt_cache

dst cache is marked as expired on the per/namespace basis by previous
path. Right now we have to implement selective cache shrinking. This
procedure has been ported from older OpenVz codebase.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 30 insertions, 1 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 67c3ed772c27..113cd2512ba7 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -699,6 +699,7 @@ static void rt_do_flush(int process_context)
 {
         unsigned int i;
         struct rtable *rth, *next;
+        struct rtable * tail;
 
         for (i = 0; i <= rt_hash_mask; i++) {
                 if (process_context && need_resched())
@@ -708,11 +709,39 @@ static void rt_do_flush(int process_context)
                         continue;
 
                 spin_lock_bh(rt_hash_lock_addr(i));
+#ifdef CONFIG_NET_NS
+                {
+                struct rtable ** prev, * p;
+
+                rth = rt_hash_table[i].chain;
+
+                /* defer releasing the head of the list after spin_unlock */
+                for (tail = rth; tail; tail = tail->u.dst.rt_next)
+                        if (!rt_is_expired(tail))
+                                break;
+                if (rth != tail)
+                        rt_hash_table[i].chain = tail;
+
+                /* call rt_free on entries after the tail requiring flush */
+                prev = &rt_hash_table[i].chain;
+                for (p = *prev; p; p = next) {
+                        next = p->u.dst.rt_next;
+                        if (!rt_is_expired(p)) {
+                                prev = &p->u.dst.rt_next;
+                        } else {
+                                *prev = next;
+                                rt_free(p);
+                        }
+                }
+                }
+#else
                 rth = rt_hash_table[i].chain;
                 rt_hash_table[i].chain = NULL;
+                tail = NULL;
+#endif
                 spin_unlock_bh(rt_hash_lock_addr(i));
 
-                for (; rth; rth = next) {
+                for (; rth != tail; rth = next) {
                         next = rth->u.dst.rt_next;
                         rt_free(rth);
                 }